Production of hydrofluoric acid.



E. S. F'ICKES.

PRODUCTION 0F HYDROFLUORIC ACID.

APPLICATION FILED MAII.3I.1914. IIENEWED Aue. 14.1918.

Patented Dec. 17, 1918.

EDWIN STANTON FICKE'S, 0F PITTSBURGH, IEENN'SYI'NIA..I I

PRODUCTION. OF HYZUEQIFLlJ'ORICl- ACID.

Specification of Letters Patent. Y

Patented Dec. 17, 1918.

` Application led March 31, 1914, Serial No. 828,436. Renewed August 14, 1918. Serial No. 249,885.

To all whom t may concern.'

Be. it known that LEDWIN S. FroKEs, a citizen of the United States, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented certain new and useful Improvements in the Production of Hydrofluoric Acid, of which the following is a full, clear, and exact description.

rihis invention relates to the production of hydrofluoric acid by the reaction of suitable reagents under heat, and its chief object is to provide an improved method and apparatus for the purpose, whereby the acid may be produced rapidly and economically on a commercial scale. To this and other ends the invention consists in the novel'features of construction and combinations of elements hereinafter described."v

Convenient and eliicient apparatus for practising the method is illustrated in the accompanying drawing, in which- Figure 1 is a longitudinal vertical section.

Fig. 2 is a sectional plan view.

Fig. 3 is a cross section on line 3-3 of Fig. l, omitting the agitator or mixer with which the apparatus is preferably equipped.

Fig. 4 is a detail cross section, on a larger scale, of the tubular retort, showing the agitator.

Fig. 5 is a detail view showing mea-ns for cooling the shaft of the agitator or mixer.

The apparatus illustrated consists, in general, of a long, tubular, stationary retort 1'0, inclosed in a suitable housing or setting 11, by which a gaseous heating medium is passed along the retort, which medium may be the hot products of combustion from a furnace or iire chamber 12. Vertical baliies 13, extending alternately from opposite sides of the setting cause the smoke and gases to take a more or less tortuous course, thereby giving a more etlicient utilization of the heat. At the end opposite the lire chamber the products of combustion iow downwardly and laterally through a flue 14 to the stack, shown in horizontal section at 15, Fig. 2.

In the present instance, the retort 10, preferably inclined downward toward the lire chamber, for example at an angle giving about a half-inch fall per foot of length, is formed of cast iron pipe-sections, the straight sections alternating with the T sections. The latter are turned up, and are provided with suitabe closures, 'as v16, removably secured by any convenient meansnot shown. These lids or closures 16 may also be'used to supis preferably made of lead or lined with lead,

is provided with a valve 21 to regulate the rate of outflow.

At its lower end the retort terminates in I a cross 22, having at the top a removable closure 23 and at the bottom a pipe 24 extending below the surface of the water in the pit 33, forming a water-seal. J ournaled in the end closures 25, 26, isa shaft 27 extending through the retort at the axis thereof and provided with helically arranged radial arms equipped at their ends with paddles or Scrapers 29 close lto, but preferably not touching, the walls of the retort. At the lower end the shaft is connected with suitable driving mechanism, as for example an electric motor 30, by means df a worm 31 and worm gear 32.

Fluorspar and sulfuric acid, mixed in suitable proportions, arev fed 4into the hot still or retort at the upper end through the hopper 18.` A In the retort it is thoroughly mixed by the revolving paddles 29, and gradually stiifens as it moves slowly down into the hotter parts. Finally it breaks up, part into powder and part into small balls or rounded lumps. Meanwhile, the reaction between the calcium iuorid and the sulfuric acid goes on, yielding hydroiiuoric acid (hydrogen fluorid,HF) in the form of vapor, and calcium 'sulfate (CaSO4) as a solid residue. The former goes oflthrough the lead pipe 20; while the residue, as fast as it reaches the cross 22, falls into the pit 33 and is removed from time to time in any convenient way. If necessary to push the residue out, the lid 23 may be removed for the purpose.

The proportions of calcium fluorid and sulfuric acid may vary widely in practice. Theoretically they should be in equal parts ('by weight) but as natural calcium iiuorid (fiuorspar) is always impure, equal parte would involve more or less Waste of the acid, as a part of the latter would simply volatil- `ize and escape. Rather less acid shoul' therefore be used. More definite proportions cannot be given, since diderent lots of fiuorspar vary greatly in impurity content, but the most economical proportions can easily be determined by analysis or trial or by both.

The temperature inside the retort or still at the hottest parts should not be less than about 315 C. (600 E), but may be increased to any degree which will not injure the retort or soften the agitator shaft so as to cause it to twist, bend, or spring. To prevent overheating of the shaft and permit higher tem eratures tobe used, the shaft may be hol ow, as in Fig. 5, to carry waterA or other cooling medium supplied to the lower end by a Vpipe 84 and discharged at the upper end by 'a pipe 35. The couplings 36 are of any suitable kind, permitting the shaft to turn. This shaft should, in most cases, revolve quite slowly. In a retort three feet in diameter and about sixty feet long the shaft should require rather more than a minute to make one revolution, and the material should require not less than about three hours (better four) to pass from the inlet to the outlet end. lf the rate of progress is too fast the mixture is heated too rapidly and causes volatilization of the sulfuric acidgithus causing aloss of fiuorin and giving a considerable amount of sulfuric acidin the hydroiuoric acid condensed. If the retort is inclined, with the inlet for the fluorspar and sulfuric acid at the higher end', the paddles or Scrapers 29 may be parallel to the axis of the retort, as the inclination of thev latter, together with the agitation produced by the paddles, will cause the material to move through the-retort'at a fast enough rate.

The hydrofluoric acid being given oif gradually as the mixture progresses, the process is in effect continuous even when the raw material is supplied intermittently..

Actual use of the invention has demonstrated its superiority over any other apparatus at the present time available for the same purpose.

It is to be understood that the invention is not limited to the apparatus and to the use herein specifically illustrated and described. rihe process described is not claimed herein, but is reserved for a later application.

l claim:

1. An apparatus for the production of hydrofiuoric acid, comprising an elongated stationary retort arranged in substantially horizontal position and composed of a plurality of cast iron sections joined end to end, a rotatable agitator extending axially iaaeaoo setting.

2. lin an apparatus for the production of hydrofluoric acid, a stationary retort of 'elongated form arranged in a substantially horizont-al position, composed. of cast iron pipe sections arranged end to end, a T section at one end, arranged with its branch turned upwardly, a closure on the upturned branch of the T provided with an outlet pipe for the continuous discharge of hydro-Y iiuoric acid gas and with means for supplying the raw material to the retort, a'section at the 'other end of the retort, havinga downwardly turned branch for the discharge of solid residue, a water-seal closing the downturned branch a ainst the escape of gas, an agitator exten ing through the retort to stir the solid contents thereof, and means to heat the retort.

3. ln an apparatus for the production of hydrotluoric acid, a stationary retort of elongated form arranged in a slightly inclined position, said retortvbein provided at one end with an outlet pipe or the discharge of hydroluoric acid gas and with means for supplying the raw materials to the retort, and provided at the other end with an outlet for solid residue, a Water-seal closing said outlet for solid residue against the escape of gas, and an agitator extending 4through the retort to stir the contents thereof, and means for heating the retort.

4. An apparatus comprising an elongated retort, arranged in a pos1tion not more than slightly inclined from the horizontal; material inlet and gas outlet at the higher end, solid material outlet at the lower end; heating means comprising a fire-place near the lower end and a Hue surrounding at least the major portion of the length of the retort and means for causin the hot products of combustion from ythe re-place to travel through said flue, in contact with the ex.- terior of said retort; agitating means comprising a rotating pipe carryin ..rabbles, and means for passing a coo lng fluid through said pipe.

5. An apparatus for making hydroiuoric acid, comprising an elongated retort comprising a plurality of sections joined tocomprising a Water-cooled rotatable pipe' a plurality of which are provided with resupported at a plurality of points in the movably secu-red man-holes and closures for 25 length of said retort, rabbles carried by said pipe, means for rotating said pipe, and means for supplying a cooling fluid to said pipe; an outlet for Solid material at the end of said retort remote from the end at which the hydrofluoric acid is Withdrawn, said outlet being provided with a Water seal; a furnace located near said outlet for solid material for heating the retort, a casing surrounding the major portion of the length of said retort, baffles in said casing in order to cause the gaseous products of combustion to assume a tortuous course; a plurality of removably secured man-holes provided in the length of said retort, and removably secured closures for said man-holes substantially as and for the purpose described.

6. An apparatus for distillation comprising an elongated retort arranged in a position not more than slightly lnclined, composedof sections joined together end to end,

Vthe same; an inlet for the material and an outlet for the products of distillation at the higher end, an outlet for the residue at the lower end, a heating means comprising a fire-place near the lower end and a flue surrounding at least the major portion of the length of the retort, mea-ns for causing the hot products of combustion from the tireplace to travel through said ue in contact with the exterior of said retort; and mechanism for continuously agitating and feeding said material through the retort comprising a shaft journaled at the ends and at one or more points along the length of the retort and provided With a plurality of rabbles thereon, and means for rotating said shaft.

In testimony whereof I -aiix my signature in the presence of the subscribing Witness.

EDWIN STANTON FICKES. Witness:

EMMA UHLINGER. 

